The purified extraction residue fraction (antigen) of microorganisms described in detail hereafter has been found to be useful in the treatment of avian leukosis as well as in the treatment of warm-blooded animals, including man, by stimulation of their immune response against a variety of tumors. The microorganism from which the purified extraction residue fraction is obtained is a pleomorphic, refractile and filterable form of bacteria which has been repeatedly isolated from both human and animal malignant tissue and blood of tumor-bearing hosts. These bacteria have been described by many investigators, but not many agree on their taxonomy because of their pleomorphism. Using standard culture and fermentation techniques, they resemble common saphophytes. Their various growth phases have been described as viruses, depetheroids, micrococci, bacilli, and fungi. See V. W-C. Livingston and E. Alexander-Jackson, "A Specific Type of Organism Cultivated from Malignancy: Bacteriology and Proposed Classification," Ann. N. Y. Acad. Sci., 174:636-654 (1970); G. J. Dominque and J. U. Schlegel, "Novel Bacterial Structures in Human Blood: Cultural Isolation," Infection & Immunity, 15:621-627 (1977); and V. W-C. Livingston and A. M. Livingston, "Some Cultural, Immunological and Biochemical Properties of Progenitor Cryptocides," Trans. N. Y. Acad. Sci., 36:569-582 (1974).
In 1970, Virginia Livingston-Wheeler and Eleanor Alexander-Jackson proposed a new taxon for this organism within the order Actinomycetale. They named the organism "Progenitor cryptocides." Progenitor cryptocides has been repeatedly isolated from human and animal malignant tumors and has many interesting features, such as pleomorphism, intermittent acid-fastness, a unique ability to pass through bacterial filters, and the ability to produce chorionic gonadotropin. See V. W-C. Livingston and E. Alexander-Jackson, "A Specific Type of Organism Cultivated from Malignancy: Bacteriology and Proposed Classification," Ann. N. Y. Acad. Sci., 174:636-654 (1970); and V. W-C. Livingston and A. M. Livingston, "Some Cultural, Immunological and Bio-Chemical Properties of Progenitor Cryptocides," Trans. N. Y. Acad. Sci., 36:569-582 (1974).
The avian leukosis complex comprises the neoplastic diseases of the hematopoietic system of the domestic chicken, together with several other neoplastic and non-neoplastic conditions which are related either etiologically or pathologically. The following diseases are included in the complex leukosis: lymphoid leukosis, erythroid leukosis, and myeloid leukosis. Diseases etiologically related to leukosis include sarcoma, neophroblastoma, endothelioma and osteopletrosis. Marek's disease includes the neural form, visceral form and ocular form. See The Merck Veterinary Manual, 3rd edition, Merck & Co., Inc., New Jersey, pp. 1081-1091 (1976). Marek's disease, for example, is seen in birds three weeks of age onward to adults. The commonest is two to four months. Young chicks are more susceptible than older birds. Genetic factors strongly influence the response of birds to agents of the leukosis complex. See A. E. Churchill and P. M. Briggs, "Agent of Marek's Disease in Culture," Nature, London 215:28-530 (1967), and J. J. Solomon, R. L. Witter, K. Nazerian and B. B. Burmester, "Studies on the Etiology of Marek's Disease: Ch. I. Propagation of the Agent in Cell Culture," Proc. Soc. Exp. Biol. Med., 127:173-177 (1968). Avian leukosis is presumably caused by a group B herpes virus. See J. J. Solomon, R. L. Witter, K. Nazerian and B. B. Burmester, "Studies on the Etiology of Marek's Disease: Ch. II. Finding of Herpes Virus in Cell Culture," Proc. Sec. Exp. Biol. Med., 127:177-182 (1968). A live but attenuated form of turkey herpes virus vaccine has been effective until recently in preventing the incidence of Marek's disease tumors; however, its effectiveness has markely declined. The mechanism of protection is not clear. Birds vaccinated develop a viremia with the vaccine. See Kermani-ARAB, V. T. Moll, B. R. Cho, W. D. Davis and Y-S. Lu, "Effect of Cyclophosphamide on the Response of Chickens to a Virulent Strain of Marek's Desease Virus," Infection & Immunity, 12:1058-1064 (1975). A group of investigators have just recently reported protection of chickens against Rous Sarcoma virus with the use of methanol extracts of BCG challenged with Rous sarcoma. They also reported that chickens with palpable tumors, and then treated, developed necrosis of the tumor. See Y. Markson, F. Doljansky and D. W. Weiss, "Effects of Prophylactic Treatment with the Methanol Extraction Residue Fraction of Tubercle Bacilli (MER) on the Development of Rous Sarcomas of Chickens Following Challenge with the Rous Sarcoma Virus," Immunological Parameters of Host-Tumor Relationships, Vol. 5, D. W. Weiss (Ed.), Academic Press, New York, pp. 51-59 (1978).
Treatment of warm-blooded animals by subcutaneous injection of the purified extraction residue fraction is based on stimulation of the immune response of the host to the injected substance. Immunotherapy is a therapeutic approach to the treatment of cancer which is based on the concept that there are distinctive antigens in or on most tumor cells that distinguish them from normal host cells. Most tumor immunologists favor the view that potentially malignant cells constantly arise in the body; but because of their foreign nature, they are normally eliminated by the body's immune system. On occasion, however, tumor cells escape this immune surveillance and continue to reproduce, resulting in cancer. The reasons for the failure of this normally efficient immune mechanism are not completely understood. The body's immune system is depressed in certain genetic immunodeficiency diseases, in various bacterial, fungal or viral infections, and in patients undergoing immunosuppressive radiation therapy.
Experimental studies in animals have demonstrated the antitumor potential of a number of immunostimulants, including live organisms of bacillus Calmette-Guerin (BCG), heat-killed cells of Cornynebacterium parvum, polynucleotides and the anthelmintic drug, levamisole.
Stimulation of host resistance may be detected in animal models that can, in fact, detect both immunostimulators and anti-cancer agents. This is accomplished by infecting warm-blooded animals, such as mice, either with a virus which produces the disease and a disease-related immunodepression or with a transplantable mammary tumor. Effective agents for their therapeutic value are recognized by their ability to restore or enhance the antibody response in the experimental animal. Another means of recognizing stimulation of the immune response is to measure increased antibody responses or increased protective effects produced by the co-administration of vaccines and "immunoadjuvants." Further discussions of the function of immune response, methods of stimulation, and testing may be found in the following references: "Stimulation of Humoral and Cellular Antibody Formation in Mice by Poly I:C," W. Turner, et al., Proc. Soc. Exp. Biol. & Med., 133, 334-338 (1970), and "Humoral and Cellular Immune Responses in Susceptible and Resistant Strains of Mice Infected with Friend Leukemia Virus," W. S. Cezlowski, et al., Proc. Soc. Exp. Biol. & Med., 146, 619-624 (1974).
The methanol extraction residue fraction of tubercle bacilli has been shown to be an activator and modulator of immunological responsiveness and capable of evoking pronounced therapeutic effects against a variety of tumors in laboratory mammals and man. See D. W. Weiss, "Nonspecific Stimulation and Modulation of the Immune Response and of States of Resistance by the MER Fraction of Tubercle Bacilli," Nat'l. Cancer Inst. Monogr., 35:157 (1972); D. W. Weiss, et al., "Nonspecific Stimulation of Antimicrobial and Antitumor Resistance and of Immunological Responsiveness by the MER Fraction of Tubercle Bacilli," in: A. Zuckerman and D. W. Weiss ( Eds.), Dynamic Aspects of Host-Parasite Relationships, Vol. 1, Academic Press, New York, p. 163 (1973).